We have a document library with incoming email settings enabled. I need to check if there is a way to get metadata sent along with the file to email address and show it up in the metadata columns in the document library. I am looking for custom metadata unlike created by or created date.
When uploading e-mail messages to SharePoint, the e-mail headers (From, To, CC, Subject, Date, etc.) can be automatically mapped to SharePoint columns.
For all header information refer this http://www.mainsoft.com/spnotes-20-doc/mappingemailheaders.
So may be your requirement cannot be achieved using OOTB feature. Since you are open to event receiver, you can attach SPEmailEventReceiver and make use of "Subject" header to fill in your metadata i.e. send the subject of the mail with information required to fill metadata separated by some pre-defined special character.
For e.g. if the subject for mail is "HR | Policy | Yes | Relocation Policy" can be read in event receiver code, split the subject by "|" and set the metadata as required :
Department - HR / 1st object of array obtained by split action Category - Policy / 2st object of array obtained by split action Confidential - Yes / 3st object of array obtained by split action Name / Title - Relocation Policy/ 4st object of array obtained by split action